Securities and Exchange Commission
                            Washington, D. C. 20549

                                Schedule 13-G
                  Under the Securities and Exchange Act of 1934

                             Radian Group, Inc.
                               Common Stock
                         CUSIP Number 750236101

Check the following box if a fee is being paid with this statement. [ ]

CUSIP No. 750236101

         1)  Name of reporting person:
                  Legg Mason, Inc.
              Tax Identification No:
                  52-1200960

         2)  Check the appropriate box if a member of a group:
                  a)  n/a
                  b)  n/a

         3)  SEC use only

         4)  Place of organization:
                  Baltimore, Maryland

      Number of shares beneficially owned by each reporting person with:
         5)  Sole voting power:          1,736,938
         6)  Shared voting power:          198,905
         7)  Sole dispositive power:        - 0 -
         8)  Shared dispositive power:   1,935,843

         9)  Aggregate amount beneficially owned by each reporting person:
               1,935,843

         10)  Check if the aggregate amount in row (9) excludes certain shares:
                 n/a

         11)  Percent of class represented by amount in row (9):
                 5.21%

         12)  Type of reporting person:
                 HC

         Item 1a)  Name of issuer:
                    Radian Group, Inc.
         Item 1b) Address of issuer's principal executive offices:
                    1601 Market Street
                    Philadelphia, PA  19103
         Item 2a)  Name of person filing:
                     Legg Mason, Inc.
         Item 2b) Address of principal business office:
                     100 Light Street
                     Baltimore, Maryland  21202
         Item 2c)  Citizenship:
                     Maryland Corporation
         Item 2d) Title of class of securities:
                     Common Stock
         Item 2e  CUSIP number:  750236101
         Item 3)  If this statement is filed pursuant to Rule 13d-1(b),
                    or 13d-2(b) , check whether the person filing is a:

         (a) [ ]  Broker or dealer under Section 15 of the Act.
         (b) [ ]  Bank as defined in Section 3(a)(6) of the Act.
         (c) [ ]  Insurance Company as defined in section 3(a)(19) of the Act.
         (d) [ ]  Investment Company registered under Section 8 of the
                    Investment Company Act.
         (e) [ ]  Investment Adviser registered under Section 203 of
                     the Investment Advisers Act of 1940.
         (f) [ ]  Employee  Benefit Plan,  Pension Fund which is
                     subject to ERISA of 1974 or Endowment Fund; see
                     240.13d-1(b)(ii)(F).
         (g) [X] Parent holding company, in accordance with 240.13d-1(b)(ii)(G).
         (h) [ ] Group, in accordance with 240.13d-1(b)(1)(ii)(H).

         Item 4) Ownership:
         (a)  Amount beneficially owned:
                1,935,843
         (b)  Percent of Class:
                5.21%
         (c)  Number of shares as to which such person has:
                  (i)  sole power to vote or to direct the vote:
                             1,736,938
                  (ii) shared power to vote or to direct the vote:
                               198,905
                 (iii) sole power to dispose or to direct the disposition of:
                            - 0 -
                 (iv) shared power to dispose or to direct the disposition of:
                             1,935,843
         Item 5) Ownership of Five Percent or less of a class:
                    n/a

         Item 6) Ownership of  more than Five Percent on behalf of another
                   person:
                    n/a

         Item 7)  Identification  and  classification  of the subsidiary which
         acquired the security being reported on by the parent holding company:

                Legg Mason Fund Adviser, Inc., as investment adviser
                  with discretion
                Legg Mason Wood Walker, Inc., as investment adviser and
                  broker/dealer with discretion
                Legg Mason Capital Management, Inc., as investment adviser
                  with discretion
                Legg Mason Trust, fsb, as investment adviser with discretion
                Batterymarch Financial Management, Inc., as investment adviser
                  with discretion

         Item 8) Identification and classification of members of the group:

                  n/a

         Item 9) Notice of dissolution of group:

                  n/a

         Item 10) Certification:

                  By signing  below I certify  that, to the best of my knowledge
         and  belief,  the  securities  referred  to above were  acquired in the
         ordinary  course of business  and were not  acquired for the purpose of
         and do not have the effect of  changing or  influencing  the control of
         the issuer of such  securities and were not acquired in connection with
         or as a participant in any transaction having such purposes or effect.

                  After  reasonable  inquiry and to the best of my knowledge and
         belief,  I certify that the  information set forth in this statement is
         true, complete and correct.

         -------------------------
         Date

         Signature

         Timothy C. Scheve, Executive Vice President, Legg Mason, Inc.
         -------------------------------------------------------------
         Name/Title



Addendum to Schedule 13G filed by Legg Mason, Inc.
Tax Identification No. 52-1200960

Shares of Radian Group, Inc. owned a/o 12/31/99

CUSIP 750236101



                                Shares    Sole     Shared     Sole     Shared
   Name                Class    Owned     V P       V P       D P       D P

                                                        

Batterymarch Financial
  Management, Inc.      IA       13,000             13,000               13,000
Legg Mason Capital
  Management, Inc.      IA      158,927            158,927              158,927
Legg Mason Fund
  Adviser, Inc.         IA    1,736,938  1,736,938                    1,736,938
Legg Mason Trust, fsb   IA          931                931                  931
Legg Mason Wood
  Walker, Inc.       BD & IA     26,047             26,047               26,047




Shares Outstanding    37,153,000

% Owned               5.21%